• 한국자기학회지
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• 제5권2호
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• pp.99-102
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• 1995

전기장 기울기 텐서가 축대칭인 결정에 대칭인 방향으로 자기장을 가하면 핵사중극공명에 미치는 Zeeman 효과에 의하여 두 개의 분리된 공명진동수가 측정된다. 이 때 가해준 자기장과 두 공명진동수 간의 차이는 서로 비례하며, ${(CH_{2})}_{6}N_{4}$ 단결정의 $^{14}N$ 원자핵에 대한 비례상수는 0.16 mT/kHz 이다. 핵 사중극 공명장치 와 개인용 컴퓨터를 interface 하여 핵 사중극 공명신호의 모습을 모니터에 표시하여 측정되는 두 공명신호의 진동수 차이로 자기장을 직접 읽을 수 있도록 하였다. 여기로부터 핵 사중극 공명 Gaussmeter를 이용하여 실험적으로 측정한 최저 자기장은 0.20 mT 였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4570-4575
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• 2023

Noise and Radio-frequency interference or RFI causes a significant restriction on the Free induction Decay or FID signal detection of the Nuclear Quadrupole Resonance procedure. Therefore, using this method in non-isolated environments such as industry and ports requires extraordinary measures. For this purpose, noise reduction algorithms and increasing signal-to-noise-and-interference ratio or SNIR have been used. In this research, sodium nitrite has been used as a sample and algorithms have been tested in a non-isolated environment. The resonant frequencies for the 150 g of test sample were measured at 303 K at about 1 MHz and 3.4 MHz. The main novelty in this study was, (1) using two types of antennas in the receiver to improve adaptive noise and interference cancellation, (2) using a separate helical antenna in the transmitter to eliminate the duplexer, (3) estimating the noise before sending the pulse to calculate the weighting factors and reduce the noise by adaptive noise cancellation, (3) reject the interference by blanking algorithm, (4) pulse integration in the frequency domain to increase the SNR, and (5) increasing the detection speed by new pulse integration technique. By interference rejection and noise cancellation, the SNIR is improved to 9.24 dB at 1 MHz and to 7.28 dB at 3.4 MHz, and by pulse integration 44.8 dB FID signal amplification is achieved, and the FID signals are detected at 1.057 MHz and 3.402 MHz at room temperature.